(Co)polymers and method for the radical (co)polymerisation of olefinically unsaturate monomers

ABSTRACT

(Co)polymers preparable by free-radical (co)polymerization of olefinically unsaturated monomers in the presence of at least one thiocarbamate-functional organic compound, processes for preparing (co)polymers by free-radical (co)polymerization of olefinically unsaturated monomers, which involves (co)polymerizing the olefinically unsaturated monomers in the presence of at least one thiocarbamate-functional organic compound, and the use of thiocarbamate-functional organic compounds as regulators in the free-radical (co)polymerization of olefinically unsaturated monomers.

The present invention relates to novel (co)polymers preparable byfree-radical (co)polymerization of olefinically unsaturated monomers.The present invention further relates to a novel process forfree-radical (co)polymerization of olefinically unsaturated monomers inthe presence of thiocarbamate-functional compounds. The presentinvention also relates to the novel use of thiocarbamate-functionalcompounds as regulators in the free-radical (co)polymerization ofolefinically unsaturated monomers.

(Co)polymers of olefinically unsaturated monomers have been known for along time and are used, for example, as thermoplastics or as importantingredients for coating materials, adhesives, and sealing compounds. Asconstituents of coating materials, adhesives, and sealing compounds, intheir function as binders, they characterize the technologicalproperties of these formulations and also the technological propertiesof the coatings, adhesive films, and seals produced from them.

In order to realize liquid coating materials, adhesives, and sealingcompounds which are easy to apply, have environmental and economicadvantages, and possess high solids contents, it is necessary to usebinders having a very low number-average and mass-average molecularweight. Their preparation by free-radical (co)polymerization, however,causes problems and cannot be effected without using regulators or chaintransfer agents.

As regulators or chain transfer agents it is customary to use thiols ormercaptans. However, these compounds give rise to a severe odornuisance, which may be manifested unpleasantly even in the (co)polymersand in the coating materials, adhesives, and sealing compounds preparedfrom them. This problem weighs particularly heavy when, for example, thecoating materials are prepared and used on an industrial scale, such asin the OEM finishing of automobiles.

It is an object of the present invention to find new (co)polymers whichno longer have the disadvantages of the prior art but which instead canbe prepared readily even with low molecular weights and without the odornuisance associated with the use of regulators or chain transfer agents.The new (co)polymers ought to be suitable in particular as binders forcoating materials, adhesives, and sealing compounds which are easy toapply, are environmentally unobjectionable, are free from unpleasantodors, and possess a particularly high solids content.

The new coating materials, adhesives, and sealing compounds ought togive coatings, adhesive films, and seals which are particularlyadvantageous both economically and technologically.

A further object of the present invention was to find a new process forthe free-radical (co)polymerization of olefinically unsaturatedcompounds which no longer has the disadvantages of the prior art butwhich instead, in a manner simple and easy to reproduce, provides(co)polymers, especially (co)polymers with low molecular weights,without the occurrence of an odor nuisance.

Yet another object of the present invention was to find new regulatorsor chain transfer agents for the free-radical (co)polymerization ofolefinically unsaturated monomers which no longer have the disadvantagesof the prior art and which in particular no longer give rise to any odornuisance during the preparation of the (co)polymers and theirapplication.

An object of the present invention not least was to find a new use forthiocarbamate-functional organic compounds.

The invention accordingly provides the novel (co)polymers preparable byfree-radical (co)polymerization of olefinically unsaturated monomers inthe presence of at least one thiocarbamate-functional organic compound,which are referred to below as “(co)polymers of the invention”.

The invention also provides the novel process for preparing (co)polymersby free-radical (co)polymerization of olefinically unsaturated monomers,which involves (co)polymerizing the olefinically unsaturated monomers inthe presence of at least one thiocarbamate-functional organic compound,and which is referred to below as “process of the invention”.

The invention provides not least for the novel use ofthiocarbamate-functional organic compounds as regulators in thefree-radical (co)polymerization of olefinically unsaturated monomers,this being referred to below as “use in accordance with the invention”.

In the light of the prior art it was surprising and unforeseeable forthe skilled worker that the object on which the present invention wasbased could be achieved fundamentally by means of the use in accordancewith the invention.

In particular it was surprising that the thiocarbamate-functionalorganic compounds for use in accordance with the invention have anoutstanding regulatory effect in the free-radical (co)polymerization ofolefinically unsaturated monomers and do not give rise to any odornuisance.

It was surprising, moreover, that on the basis of the use in accordancewith the invention and of the process of the invention the (co)polymersof the invention were obtained, which were substantially or entirelyfree from unpleasant odors and possessed outstanding performanceproperties.

Furthermore, it was surprising that the (co)polymers of the inventionwere outstandingly suitable as binders for coating materials, adhesives,and sealing compounds, especially for liquid coating materials,adhesives, and sealing compounds having particularly high solidscontents of up to 100% by weight (100% systems).

The coating materials, adhesives, and sealing compounds of the inventionin question were surprisingly free from unpleasant odors, were easy andeconomic to apply, and on a wide variety of substrates gave coatings,adhesive films, and seals which were particularly advantageous botheconomically and technologically.

The thiocarbamate-functional organic compounds for use in accordancewith the invention contain at least one, preferably at least two, and inparticular two, thiocarbamate groups. The thiocarbamate-functionalorganic compounds for use in accordance with the invention are referredto below for the sake of brevity as “thiocarbamates”.

In addition, the thiocarbamates may contain at least one furtherfunctional group. This further functional group is selected such that itdoes not induce any unwanted secondary reactions and/or does not inhibitthe free-radical (co)polymerization of the olefinically unsaturatedmonomers and/or the regulatory effect of the thiocarbamates. Preferably,the further functional group is selected such that it is able to undergocrosslinking reactions with the crosslinking agents that may be presentin the coating materials, adhesives, and sealing compounds of theinvention. With particular preference, hydroxyl groups are used asfurther functional groups.

The thiocarbamates are preferably organic compounds of low molecularmass, i.e., compounds which are not composed of monomer units.

The thiocarbamates are conventional compounds and can be prepared bymeans of the conventional methods and techniques of organic chemistry.They are preferably prepared by reacting an organic compound containingat least one, preferably at least two, and in particular two, isocyanategroup(s) (called “isocyanate” below) with at least one, especially one,thiol.

The isocyanate is preferably selected from the group of thediisocyanates.

Examples of suitable diisocyanates are isophorone diisocyanate (i.e.,5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane),5-isocyanato-1-(2-isocyanatoeth-1-yl)-1,3,3-trimethylcyclohexane,5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclo-hexane,5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane,1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane,1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane,1-isocyanato-2-(4-isocyanatobut-1-yl)cyclohexane,1,2-diisocyanatocyclobutane, 1,3-diiso-cyanatocyclobutane,1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane,1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane,1,4-diisocyanatocyclohexane, dicyclohexylmethane 2,4′-diisocyanate,trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylenediisocyanate, hexamethylene diisocyanate, ethylethylene diisocyanate,trimethylhexane diisocyanate, heptamethylene diisocyanate ordiisocyanates derived from dimer fatty acids, as sold under thecommercial designation DDI 1410 by Henkel and described in patents WO97/49745 and WO 97/49747, especially2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentylcyclohexane, or 1,2-, 1,4-or 1,3-bis(iso-cyanatomethyl)cyclohexane, 1,2-, 1,4- or1,3-bis(2-isocyanatoeth-1-yl)cyclohexane,1,3-bis(3-isocyanatoprop-1-yl)cyclohexane, 1,2-, 1,4- or1,3-bis(4-isocyanatobut-1-yl)cyclohexane, liquidbis(4-isocyanatocyclohexyl)methane with a trans/trans content of up to30% by weight, preferably 25% by weight, and in particular 20% byweight, as described in patents DE 44 14 032 A1, GB 1 220 717 A1,DE-A-16 18 795 or DE 17 93 785 A1; tolylene diisocyanate, xylylenediisocyanate, tetramethylxylylidene diisocyanate (TMXDI), bisphenylenediisocyanate, naphthylene diisocyanate or diphenylmethane diisocyanate.

Particular preference is given to using aliphatic isocyanates,especially the aliphatic diisocyanates. Aliphatic isocyanates areisocyanates in which the isocyanate groups are attached to aliphaticcarbon atoms.

The thiols are preferably monothiols, which where appropriate may alsocontain at least one of the further functional groups described above.

Examples of suitable thiols are methyl, ethyl, propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, andphenyl mercaptan and 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl,5-hydroxypentyl, and 6-hydroxyhexyl mercaptan. Particular preference isgiven to using 2-hydroxyethyl mercaptan (2-mercaptoethanol).

The isocyanates and the thiols can be used in equimolar amounts.Preferably, however, a molar excess of thiols is employed. Unreactedthiols are then separated off after the reaction from the thiocarbamatesformed. Examples of suitable separation techniques are extraction,distillation, and filtration.

For the reaction the customary and known apparatus and safety measuresare employed, as envisaged for the handling of isocyanates.

For the process of the invention it is possible to use any conventionalolefinically unsaturated monomers which can be free-radically(co)polymerized. Examples of suitable olefinically unsaturated monomersare described in detail in German patent application DE 199 30 664 A1,page 4 line 28 to page 9 line 49, or in German patent application DE 10017 653 A1, page 7 line 64, paragraph [0086], to page 9 line 40,paragraph [0092].

The process of the invention may be conducted conventionally in bulk,solution, emulsion or dispersion. As reactors for the process theconventional stirred tanks, stirred tank cascades, tube reactors, loopreactors or Taylor reactors are suitable, as are described, for example,in patents DE 198 28 742 A1 or EP 0 498 583 A1 or in the article by K.Kataoka in Chemical Engineering Science, Volume 50, number 9, 1995,pages 1409 to 1416. The free-radical copolymerization is preferablyconducted in stirred tanks or Taylor reactors, the Taylor reactors beingconfigured such that the conditions of Taylor flow are met along theentire length of the reactor, even if the copolymerization causes thekinematic viscosity of the reaction medium to undergo a sharp change,especially an increase (cf. German patent application DE 198 28 742 A1).

The process of the invention is advantageously conducted at temperaturesabove room temperature and below the lowest decomposition temperature ofthe respective monomers used, the temperature range chosen beingpreferably from 10 to 150° C., with very particular preference from 30to 120° C., and in particular from 40 to 110° C.

When using particularly volatile monomers the process of the inventionmay also be conducted under pressure, preferably under from 1.5 to 3000bar, more preferably from 5 to 1500 bar, and in particular from 10 to1000 bar.

The molar ratio of thiocarbamates to olefinically unsaturated monomersmay vary very widely and is guided by the requirements of the case inhand, in particular by the intended molecular weight of the (co)polymersof the invention. The molar ratio is preferably from 10⁻¹ to 10⁻⁴, inparticular from 10⁻² to 10⁻³.

As far as the molecular weight distribution is concerned, norestrictions whatsoever are imposed in the (co)polymers of theinvention. Advantageously, however, the process of the invention isconducted so as to give a ratio M_(w)/M_(n), measured by gel permeationchromatography using polystyrene as standard, of ≦4, preferably ≦2, andespecially ≦1.6.

EXAMPLES Preparation Example 1

The Preparation of a Thiocarbamate

A glass reaction vessel was charged with 10 g (127.9 mmol) of2-mercaptoethanol and this initial charge was heated to 40° C. undernitrogen. At this temperature, 1.56 g (6.34 mmol) oftetramethylxylylidene diisocyanate (TMXDI) were added with stirring. Theresulting reaction mixture was stirred at 40° C. for 24 hours and thenpoured into 200 ml of ice-water. The white precipitate was filtered offand washed with deionized water until completely odor-neutral. Theprecipitate was then dried at room temperature under an oil pump vacuum.

Elemental analysis gave the following composition in % by weight:Element: N C H S found: 6.92 53.62 7.06 16.05 calculated: 6.99 53.987.05 16.01

The structure of the thiocarbamate was confirmed by nuclear magneticresonance spectroscopy:

¹³C NMR, 100 MHz, DMSO-d₆, δ [ppm]:

30.8 (C-8, C-8′, C-9, C-9′, primary), 31.66 (C-11, C-11′, secondary),57.33 (C-7, C-7′, quaternary), 61.54 (C-12, C-12′, secondary), 121.41(C-2, tertiary), 122.7 (C-4, C-6, tertiary), 127.89 (C-5, tertiary),147.49 (C-1, C-3, quaternary), 164.38 (C-10, C-10′, quaternary).

¹H NMR, 400 MHz, DMSO-d₆, δ [ppm]: 1.53 (s, 12H, C^(8,8′,9,9′H) ₃), 2.76(t, 4H, C^(11,11′)H₂), 3.39 (q, 4H, C^(12,12′)H₂), 4.84 (t, 2H, OH),7.09-7.12 (m, 2H, C^(4,6)H), 7.18-7.22 (m, 1H, C⁵H), 7.26 (m, 1H, C²H),8.37 (s, 2H, NH)

Examples 1 to 3 and C1 (C=Comparative)

The Free-Radical Polymerization of Styrene in the Absence (Example C1)and in the Presence (Examples 1 to 3) of the Thiocarbamate fromPreparation Example 1

General Experimental Protocol

On an analytical balance, the desired amount of the thiocarbamate frompreparation example 1 was weighed into a 50 ml Schlenk tube anddissolved in 15 ml of tetrahydrofuran. The styrene solution, containinginitiator, was then added under nitrogen. Residual traces of oxygen wereremoved by evacuating and charging with nitrogen several times. Thestyrene solution was in each case prepared fresh directly before use.This was done by distilling the styrene under reduced pressure on acolumn at 30° C. under inert gas, to remove the stabilizer, and thenadding azoisobutyronitrile (AIBN) to give a 0.1 molar solution.

For each experimental series, four Schlenk tubes were set up inparallel, their contents differing from one another in terms of theratio of thiocarbamate to styrene (examples 1 to 3 with thiocarbamate,example C1 without thiocarbamate). The sealed Schlenk tubes were thenheated on a water bath at 55° C. for 3 hours. The proportions used werethose listed in table 1. TABLE 1 The amounts of styrene andthiocarbamate used Styrene Thiocarbamate solution (S) (TCA) TCA/SExample [g] [mmol] [g] [mmol] [molar] C1 18.02 173 — — 0 1 18.06 173.40.2294 0.5727  3.3 * 10⁻³ 2 18.07 173.5 0.4771 1.1911  6.9 * 10⁻³ 318.06 173.4 0.9324 2.3278 1.34 * 10⁻²

After the end of the polymerization, the reaction mixtures were eachpoured into 300 ml of cold methanol. The white polymers precipitatedwere isolated by filtration and dried under reduced pressure. The molarmasses of the polystyrenes were determined by means of gel permeationchromatography using polystyrene as standard. The results can be foundin table 2. TABLE 2 Conversion (%), number-average molecular weightM_(n) [daltons], average degree of polymerization P_(n), and molecularweight polydispersity M_(w)/M_(n) Example Conversion Mn Pn Mw/Mn C1 7.5143 945 1 382 1.47 1 7.0  75 467   725 1.53 2 7.2  46 244   444 1.43 37.9  26 150   251 1.42

The results underline the fact that the thiocarbamate is highly activeas a regulator or in transfer agent.

1. A (co)polymer comprising a free-radical (co)polymerization product ofat least one olefinically unsaturated monomers prepared in the presenceof at least one thiocarbamate-functional organic compound.
 2. The(co)polymer as claimed in claim 1, wherein the thiocarbamate-functionalorganic compound contains at least one thiocarbamate group.
 3. The(co)polymer as claimed in claim 2, wherein the thiocarbamate-functionalorganic compound contains at least two thiocarbamate groups.
 4. The(co)polymer of claim 1, wherein the thiocarbamate-functional organiccompound comprises a reaction product of an organic compound containingat least one isocyanate group and at least one thiol.
 5. A process forpreparing the (co)polymer of claim 1 comprising (co)polymerizing the atleast one olefinically unsaturated monomers in the presence of the atleast one thiocarbamate-functional organic compound.
 6. The process asclaimed in claim 5, wherein the thiocarbamate-functional organiccompound contains at least one thiocarbamate group.
 7. The process asclaimed in claim 6, wherein the thiocarbamate-functional organiccompound contains at least two thiocarbamate groups.
 8. The process ofclaim 5, wherein the thiocarbamate-functional compound comprises areaction product of an organic compound containing at least oneisocyanate group and at least one thiol.
 9. A method comprisingregulating free-radical (co)polymerization of at least one olefinicallyunsaturated monomers by adding a thiocarbamate-functional organiccompound to the (co)polymerization.